Machine and method for producing a three dimensional lattice

ABSTRACT

A machine for making a three dimensional lattice array of strands within a grid framework. The strand lattice can be utilized as a reinforcement for other materials. The method of making the three dimensional lattice involves sewing strands in three directions within a grid framework.

[45 1 May 20, 1975 United States Patent [1 1 Amos 3,778,492 12/1973 Lemmons..t.................... 264/158 X MACHINE AND METHOD FOR PRODUCING A THREE DIMENSIONAL LATTICE Inventor:

Primary ExaminerFrancis S. Husar Amos, Palm Springs, Assistant Examiner-Car1 Rowold Cahf' Attorney, Agent, or Firm.1. G. Heimovics; D. S.

Olexa; S. L. Epstein Brunswick Corporation, Skokie, 111.

May 6, 1974 [73] Assignee:

22 Filed:

ABSTRACT [21] Appl. No.: 467,065

Related US. Application Data Division of Ser. No. 272,736, July 18, 1972, Pat. No. 3,822,463.

A machine for making a three dimensional lattice array of strands within a grid framework. The strand lattice can be utilized as a reinforcement for other materials. The method of making the three dimensional lattice involves sewing strands in three directions within a grid framework.

[58] Field of Search 425/275; 249/205 5 Claims,

24 Drawing Figures [56] References Cited UNITED STATES PATENTS 3,322,868 5/1967 Kruse et 161/144 X Ema PATENTED HAY 20 i975 SHEET 1 OF 8 PATENIEB HAY 2O IHTS SHEET 5 BF 8 PATENIEDHAYZUIBYE QQBB HMS SHEET 8 BF 8 [III I [Ill/n n W I n n n Lni W, i i

PATENTED HAY 2 0 I975 SHEET 8 BF 8 MACHINE AND METHOD FOR PRODUCING A THREE DIMENSIONAL LATTICE This application is a divisional application of my copending application, Ser. No. 272,736, filed July 18, 1972 issued as US. Pat. No. 3,882,463, on July 9, 1974. Y

FIELD OF THE INVENTION This invention relates to strand lacing machines, and more particularly, to sewing machines capable of making a three dimensional lattice array of strands.

BACKGROUND OF THE INVENTION Many material forms are used today as composite materials in order to take advantage of the best properties of the different materials forming the composite. Fabric reinforced plastic resins are one class of such composite materials in wide use. Complicated designs have been employed to utilize the two dimensional limitations of the fabric in order to produce three dimensional shapes. There are many problems in producing i a three dimensional shape from a two dimensionally reinforced material; for examaple, a laminated glass fabric-plastic resin composite can delaminate just like paint peeling off a house because the composite is not reinforced in all three dimensions. ,Thus, the obvious need for three dimensionally reinforced composite materials exists.

In order to provide a three dimensionally reinforced product, it is first necessaryto provide a lattice of strands or yarns in a three dimensional array. One attempt to make such a three dimensional strand array is taught in U.S. Pat. No. 3,322,868, wherein two rather crude devices are used in combination. The first device provides a pluralityof parallel strands on a structure,

similar to a picture frame. Multiple frames are then alternately stacked to provide groups of strands that are perpendicular to each other. A second device having a plurality of semi-circular pointed needles, each having a single strand or yarn', is used in conjunction with positioning rods to lace the strands of the frames in only the third dimension. These two devices require a great deal of hand operation to provide an awkward lattice array that 1) does not have uniform or preselected pretensioning of the strands; (2) is unreliable to provide reproducibility in lattice arrays; (3) is lacking in uniformity; and, (4) is uneconomical to use.

SUMMARY OF THE INVENTION The invention contemplated and disclosed herein provides a new, novel and unique sewing machine that produces a substantially uniformly prestressed three dimensional strand lattice that has the attributes of being reliable, reproducible, uniform, economical and achieves solutions to the problems that the prior art has left unsolved. Such a machine utilizes new and novel sewing needles which operate in conjunction with a I new and novel grid framework structure that supports Still another object of this invention is the provision for producing a three dimensional lattice array of strands wherein the strands are in a substantially orthogonal configuration.

Yet another object of this invention is the provision for an open grid framework structure that can have a three dimensional array of substantially equally tensioned strands sewn therein.

And still another object of this invention is the provision for a new type of sewing needle.

Still yet another object of this invention is to provide a method for making a three dimensional lattice array of strands in an open grid framework structure.

A feature of the invention is the provision for a needle that sews a plurality of threads.

Another feature of the invention is the provision for a grid framework structure wherein very fine flexible strands support the sides of the grid box.

Yet another feature of this invention is the provision for rigid and/or flexible hooks that secure the strands to the grid box.

Still another feature of the invention is the provision for substantially equally tensioning a plurality of strands that are sewn by such a machine using only a single tensioning device.

And still another feature of the invention is the provision for means that secure the sides of the grid surfaces to form a grid structure box and also provide for uniformly feeding the grid box in the machine.

A structural grid box formed with open grid surfaces is placed onto the table of machine. A strand attaching means or clip is used to fasten all the strands or yarns to the grid box; the strands coming from the plurality of needles secured to the machine. The grid box is placed in position with respect to the needles at the start of the operation. During operation, the needles moving forward enter the openings in the grid box sewing the strands that are secured to grid surface opposite to where the needles enter, and then the needles are withdrawn from the grid box which is automatically advanced with the sewing cycle repeated. When the sewing operation in one direction is completed, the strands are fastened to the grid box and cut therefrom. The grid box is repositioned on the machine in a second orientation and theme third orientation so that sewing of the second and third directions may take place in a manner similar to that of the first direction. Thus, upon completion, the grid box contains a three dimensional lattice array of strands.

The above and further objects and features will be more readily understood by the reference to the following detailed description and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partial end elevation view of part of the machine portion of one embodiment of the invention; FIG. 2 is a partial side elevation view of part of the machine portion of one embodiment of the invention;

FIG. 3 is a partial side elevation view of the feeding device for the strand holding means for one embodiment of the invention;

FIG. 4 is a partial side elevation view of the strand guide and strand tensioning device portion of the invention;

FIG. 5 is a partial end elevation view of the strand guide of the invention;

FIG. 6 is a segmented view of one part of the grid box portion of one embodiment of the invention;

FIG. 7 is a cross sectional segment view of a portion of the grid box on the feed table in contact with the feeding device of one embodiment of the invention;

FIG. 8 is a perspective view of an assembled grid box of one embodiment of the invention;

FIG. 9 is a partial sectional view of the driving mechanism for the feeding device portion of one embodiment of the invention;

FIG. 10 is a perspective view of a corner bracket for the grid box portion of one embodiment of the invention;

FIG. 11 is a side elevation view of a comer bracket of the grid box portion of one embodiment of the invention;

FIG. 12 is a side elevation view of a corner of a grid box wall of one embodiment of the invention;

FIG. 13 is a segmented cross section view of one grid box surface of one embodiment of the invention;

FIG. 13a is a segmented cross section view of a portion of one grid box surface and needles of one embodiment of the invention;

FIG. 14 is a segmented cross section view of a portion of one grid box surface of one embodiment of the invention;

FIG. 15 is a cut away perspective view of one embodiment of the invention;

FIG. 16 is a segmented cross section view of a portion of one embodiment of the invention;

FIG. 17 is a segmented cross section view of a portion of one embodiment of the invention;

FIG. 18 is a perspective view of the needle point of one embodiment of the invention;

FIG. 19 is a segmented cross section view of one grid surface and the needles during the sewing of one grid of one embodiment of the invention;

FIG. 20 is a segmented cross section view of the grid surface and the needles wherein the sewing has progressed farther than FIG. 19 and depicting one embodiment of the invention;

FIG. 21 is a segmented cross section view of one grid surface and the needle wherein the sewing has progressed farther than FIG. 20 and depicting one embodiment of the invention;

FIG. 22 is a segmented cross section view of one grid surface and the needles on the upstroke of one embodiment of the invention;

FIG. 23 is a perspective view of another embodiment of the invention; and

FIG. 24 is a segmented cross sectional view of the needle and the upper grid surface of one embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In a preferred embodiment, the basic parts of the machine comprise a feed table having a feeding means mounted thereon; a set of needles mounted on a slide that has a reciprocating motion with respect to the table; and, a yarn or strand tensioning device that is co operatively mounted with respect to the needles. A necessary adjunct to the machine is a grid box comprising foraminous grid surfaces with the box being held together by rods that function cooperatively with the feeding means to move the grid box through the machine in a preselected time sequence. The grid box is capable of being fed into the machine and sewn by the needles; the box maintains the strands in a three dimensional array. The needles and the strand tensioning device function to provide substantially equal tension in all the strands during sewing.

As used herein, the term strand includes wire, thread, yarn, monofilament, cable, etc.; all are used interchangeably and are contemplated to mean an elongated flexible element capable of being fed through the needles and the grid box to form a three dimensional lattice array.

In the operation of the machine, an assembled grid box is positioned on the feed table with the starting ends of the strands or yarns secured to the grid box such as by a yarn clip. The feeding means attached to the table moves the grid box along the machine table in a preselected time sequence of move and dwell. During the dwell portion of the time sequence the needles with the strands of yarns therein enter the grid box surface nearest thereto, passing into and through the grid box and just past the far surface of the opposite grid box surface. The needles have special points to cooperate with the strand holding means mounted on the far side grid surface in order to loop and secure the strands thereto. After the threaded needle has been withdrawn from the grid box, the grid box is indexed to its next position and at the same time the strands from the needles partially pass over the near side of the grid surface. These strands are positioned by strand guides located on the exterior of the near side grid boxsurface. When the grid box has been moved to the next position, and during the dwell portion of the timing sequence, the needles again enter the grid box thereby completing the first sewing pass and staring the second sewing pass of the strands. This operation is repeated until the grid box is completely sewn in one direction. The strands are secured to the grid box such as by a yarn clip and then cut, thus completing the sewing operation in one direction, or for ease of understanding the X direction. The grid box is rotated on the table and again fed into the machine. The strands are secured to the edge of the grid box and the grid box is, for a second time, indexed along the feeding table with the needle sewing repeated. Upon completion of the sewing operation, the strands are again secured to the box and cut, completing the sewing the second or Y direction. The grid structure is then rotated for a second time on the grid table and fed through the machine with the strands sewn in the same fashion as before, thereby completing sewing in the third or Z direction. Thus, a three dimensional lattice array of strands completely fills the interior of the grid box. Since the grid box is a substantially rigid structure, the needles operate in the same fashion during the total sewing operation and the strand tensioning device is mounted with the needles on the needle mount to operate continuously and cooperatively; all parts function to insure that all strands are all substantially equally tensioned as they are sewn.

The invention also contemplates the method of making an open surface grid box having a three dimensional lattice array of strands internally contained therein, with all strands substantially equally tensioned, by the steps of the operation broadly described herein above. The basic steps are feeding a grid box into the machine, sewing the strands with substantially equal tension throughout the grid box in three different directions, and securing the end of the strands to the grid box in order to provide substantially equal tension on all the strands.

THE GRID BOX In a preferred embodiment of the invention, a grid box 500, shown in FIG. 8, comprises oppositely spaced foraminous grid walls 510 and 520. The internal surfaces of the grid walls SW and 520 are flat with the exterior surfaces providing hooks and notches for the strands, as shown in FIG. 6. The grid walls 510 and 520 are used in pairs being oppositely spaced apart in forming the grid box 500. The grid walls 510 and 520 are of substantially rigid frameworks and may be formed of interlocking strips 511 and 512; and, 521 and 522 which define passages 514 and 524 and the interior and exterior grid surfaces. The strips 511, 512, 521 and 522 have outwardly projecting undercut ends 515, 516, 525 and 526, as shown in FIGS. 6, 7 and 12. On each of the strips 512 of the grid wall 510 there are notches 518 to accommodate the positioning of the strand during the sewing operation. On each of the strips 521 of the grid wall 520 there are lugs 530 secured thereto. The lugs 530 have ears 531 to provide a means for hooking the strands during the sewing operation. The tips 532 of the ears 531 are recessed with respect to the exterior surface 520a of the grid wall 520, as shown in FIGS. 14, I5 and 16. The ears 531 of adjacent lugs 530 are spaced apart as shown in FIGS. 6 and 7. Corner brackets 540 with legs 541 are secured to each corner of the grid walls 510 and 520 where the undercut ends 515, 516, 525 and 526 have been removed, as shown in FIGS. 6, 7, 8, 10, 11 and 12. The dogs 542 of the corner brackets 540 are at an angle with respect to the legs 541 and not in the same plane therewith; as shown in FIGS. and 11. l

The grid box 500 is assembled by inserting undercut ends 515, 516, 525 and 526 of the grid walls 510 and 520 into the undercut grooves 551 of the edge rods 550,. In forming the grid box 500 the grid walls 510 and 520 are positioned opposite to each other with the notches 518 and lug 530 facing outwardly. A second series of grooves 552 on the rods 550 are aligned with the center of the grid passages 514 and 524. The three adjacent dogs 542 of the corner brackets 540 are fastened together with snap rings 543, as shown in FIGS. 6 and 8. The dogs 542 do not extend beyond the edges formed by the rods 550. For proper operation,,the openings 514 and.524 must be alinged and the rows of lugs 530 must be parallel to the notches 518 when the surfaces are opposite each other. It is contemplated that the grid passages or openings 514 and 524 may be square, rectangular, triangular, pentagonal, etc., as desired. Rather than forming the grid surfaces 510 and 520 by interlocking strips, it is fully contemplated that the grid surfaces may be cast or formed in any desired manner.

It has been found necessary that the edge rods 550 form planar surfaces but the grid surfaces 510 and 520 attached thereto do not necessarily have to be planar. The grid surfaces 510 and 520 can be any desired shape as long as they do not extend beyond the planar surfaces defined by the edge rods 550.

Alternatively, resiliently flexible lugs 530a with car portions 531a, as shown in FIG. 16, may be used in place of the rigid lugs 530. Also, lug 530b having movable ear portions 531b may be used as shown in FIG. 17, wherein the cars 5311; are mounted on shafts 532k which can rotate in such a fashion to release the hooked strands.

The use of the assembled grid box 500 as it cooperatively functions with the machine will be discussed hereinafter in more detail.

THE MACHINE In a preferred embodiment of the machine as shown in FIGS. land 2, the frame 10 supports a feed table 20 which is mounted thereon. A pair of upper slideways l3 and a pair of lower slideways 12 are mounted on and secured to the frame 10 in a space relation to the table 20. The slideways l2 and 13 are shown covered with dust protectors 12a and 13a. Flywheel 30 is rotatably mounted on shaft 33 that is journal mounted 37 on the frame 10 at 32. The flywheel 30 is located between the slideways 12 and 13. The shaft 33 is connected to a prime mover, such as a motor (not shown) by means of sprockets and a chain (not shown), thereby providing motion for the operation of the machine. A counterbalance 35 is slideably mounted on the upper ways 13 and obtains reciprocating motion via the upper connecting rod 34 which is pivotally mounted on the flywheel 30 at 340 and on the counterbalance 35 at 34b. The needle holder 40 is slideably mounted on the lower guideways l2 and pivotally connected to the flywheel 30 by the lower connecting rod 36 at 36a and to the needle holder 40 at 36b. As the flywheel 30 revolves, the needle holder 40 moves back and forth or upwards and downwards, as the case may be, in a reciprocating motion. At the same time, the counterbalance 35 moves in an opposite direction to the needle holder 40 to provide smooth and substantially vibrationless motion. A strand tensioning device 50 is mounted on the needle holder 40 and operates to pull the multiple strands from a strand or yarn creel (not shown) during both the upward motion of the holder 40.

The strand 700 enter through the strand guides 752 secured to the guide plate 751 that is part of the strand guide assembly 750 mounted on the frame 10 at 753, shown in FIGS. 4 and 5. The strands 700 passed under the roll 754 and then passes up and over the dancer roll 704 that is part of the strand tensioning assembly 50. The strand tensioning assembly 50 is mounted on the movable needle mount 40 while the strand guide assembly 750 is stationary. The: dancer roll 704 is rotatably mounted on cantilevers 705 that are secured to the partially rotatable spring tensioned shaft 706. The

spring 708 and the coupler'708a fastened to shaft 706 tend to cause counterclockwise rotation thereof which in turn cause the dancer roll 704 to rotate in a counterclockwise direction around the shaft 706. Cam 709 secured to shaft 706 and the cam keeper 710 secured to the movable needle mount 40 insures only partial counter-clockwise rotation of the shaft 706 and dancer roll 704. Clockwise rotation of the dancer roll 704 about the shaft 706 causes an increased load on the spring 708 which functions to restrain such rotation. As explained hereinafter, the semi-rotational confinement of the dancer roll 704 is what provides substantially equal tension on all the strands as the lattice is formed.

The grid pusher assembly 210 is mounted at the side and underneath the feed table 20, and driven by drive assembly 21 as shown in FIGS. 1, 2, 3 and 9. Assembly 21 comprises pairs of bevelled gears at each end of shaft 21a; one end thereof coupled to and being driven by the drive shaft 33 and the other end transferring the power for the grid pusher assembly 210. As shown in FIGS. 3 and 9, the grid pusher assembly 210 has eccentric shaft 231 that is driven by the drive assembly 21 which is'coupled by timing and power transmission gears 233 to the cam shaft 232. Suitable journal bearings 234 are mounted on frame 10 to support shafts 231 and 232. Pusher arm 211 is eccentrically mounted on shaft 231 at 213. At the other end of the pusher arm 211 is a pawl 212 which reciprocatively moves back and forth as the shaft 231 is rotated. The upward pusher assembly 220 is mounted on the frame 10 adjacent the pusher arm 211 and connected thereto by coupler 227. Cam 221 is mounted on shaft 232 and engaged by cam follower 222 which is part of linkage 223 that is pivotally mounted on the frame 10 at 226 and pivotally connected to the coupler 227 at 224. The coupler 227 is pivotally connected to the arm 211 at 225. As cam shaft 232 rotates, the cam follower 222 imparts an up and down motion to the pusher arm 211 that is translated by the linkage 223 in cooperation with the coupler 227. Thus, the combined motions from the eccentrically mounted pusher arm 221 and the cam follower 222 coupled thereto cause the pawl 212 to rise above the top surface of the table through hole 214; move forward; withdraw below the top surface of the table 20; oscillate back and forth; and, again rise above groove 552 of the rod 550 is shown in FIGS. 3 and 7.

A friction brake 45, shown in FIGS. 1 and 2, is

. mounted on feed table 20 and engages the sides of the grid box 500 to prevent overfeeding. However, other types of brakes are contemplates, such as a device similar to the grid pusher assembly 210 but operating in a reverse fashion to prevent the grid box 500 from moving during the dwell portion; and will be well understood by those skilled in the art.

A dual set of pressure rolls 70 is mounted on a framework 71 that is attached to the frame 10 and the feed table 20. One set of rollers 70 is located in front of and just adjacent to needle 60 at the feed-in section of the machine on table 20. The second set of rollers 70 is located between the needles 60 and the upright portion of the frame 10. Both sets of rollers are adjusted to a preselected height to create a slight pressure on the rod 550 of the grid box 500 as it is automatically fed to the machine to prevent the grid box 500 from lifting up from the table 20 during the sewing operation.

In another embodiment of the invention, the feed table can be slidably mounted on the frame and indexedly moved or advanced by a feeding device similar to the grid pusher assembly 210. This would permit the grid box to be secured to the feed table with both the table and the grid box thereon advancing past the needle mount 40 during the reciprocating motion thereof.

Alternatively, in another embodiment of the invention, the grid box can be secured to the table 20 and the needle mount slidably mounted on the frame 10 so that after every reciprocating motion thereof, the mount is advanced with respect to the grid box by a feeding device similar to the grid pusher assembly.

In yet another embodiment of the invention, it is contemplated that the grid box'can be mounted in such a manner as to be provided with a forward and back motion for sewing with the needles in the needle mount held stationary. In this embodiment either the grid box or the needle mount can be slidably advanced. These order embodiments will be well understood by those skilled in the art. All of these embodiments provide relative motion between the grid box and the needles to insure a satisfactory sewing operation of the total grid.

THE NEEDLES The butt or proximal ends 601 of the needle 60 are secured to the moveable needle mounts 40 with mounting brackets 610 as shown in FIG. 4. The point or distal end 602 of the needle 60 may be fashioned to sew one or more strands as shown in FIG. 18. The needle point 602 has a rather sharply tapered side portion 606 converging at the tip 614. Extending rearwardly toward the butt end 601 are undercut slots 640 on both sides of the needle 60. The web 611 formed by the slot 604 must be thinner than the distance between the ears 531 of the lug 530. Gradually tapered top and bottom portions 606a of the point 602 form the other portions of the needle point 602 which converge at the tip 614. The slots 604 provide a flat portion 613 with a further tapered curvilinear undercut portions 612 formed towards the tip 614. A tapered flat portion 609 is located between the tip 614 and the portion 612. Strand holes 603 open onto the portion 612 with the axis of the hole 603 projecting rearwardly at any angle, and preferably about a 30 angle. The holes 603 open on the bottom side 615 of the needle 60 which is actually the leading surface wherein the holes 603 cooperate with strand grooves 608 that project rearwardly toward the butt end 601. On the upper side 616 of the point 602 are strand slot grooves 607 that project rearwardlyand intersect and cooperate with the slots 605. It has been found desirable to offset the holes 603 with respect to the slots 605 wherein the slots 605 are closer to the sides 617 of the needle 60. During the forward stroke of the needle 60, the strand 700 is in a position whereby it passes through the hole 603 and around the slot 605 extending rearwardly in grooves 607 and 608.

OPERATION In making a three dimensional lattice array of strands, strands 700 from a creel are fed through the strand tensioning device 50 as described hereinabove, and threaded through the needle holes 603, around the point 602 and back through the slots 605. An assembled grid box 500 is placed on the feed table 20 so that the grid wall 510 with notches 518 is adjacent the nee dles 60 with the opposite grid wall 520 next to the table 20 with the ears 531 of the lugs 530 projecting towards the table. The needles 60 and the needle mount 40 are moved to a full upright, back or withdrawn position above or outside the grid box 500 and exterior to the grid wall 510, similar to FIG. 22. The strands 700 from the needles 60 are initially secured to the grid wall 510 in the slot 560, as shown in FIG. 6, by a U-shaped spring clip (not shown). Alternatively, initial securing of the strands to the box 500 may employ such simple means as taping the strands to the box, or more sophis- .positioned on table under the first set of pressure holddown roller 70 in such a manner that the pawl 212 contacts the first of the series of rod 550 grooves 552. The brake 45 is clamped on the sides of the grid box 500.

The machine is started by the prime mover with the needles 60 aligned with respect to entering the opening 514 of the grid surface 510. As the needles enter the grid surface 510 the notches 518 align the strands 700, as shown in FIG. 13a. As the needles 60 with the surface 615 leading and the surface 616 trailing move through the grid surface 510 toward the grid surface 520 the strands 700 are pulled by the needles 60 motion and under substantially equal tension created by the dancer roll 704 in cooperation with the spring tension shaft 706. As the double stranded needles 60 pass through the openings 524 from the interior of the grid box 500, the strands 700 come into contact with the ears 531 and are displaced inwardly from the holes 603 andthe slots 605 toward the web 611, as shown in FIG. 19. Near the end of the forward stroke of the machine, as the needles 60 continue to move through the openings 524 of the grid wall 520 to a position where the needle holes 603 and the needles slot 605 have cleared the ears 531, the strands 700 are automatically pulled back to the normal position, as shown in FIG. 20. This return to the normal position occurs through the cooperative action of the dancer roll 704 and the spring tension shaft 706. As the needles 60 start on their backstroke to pull upward through the grid box 500, the strands 700 are hooked or looped on the undercut portions 533 of the ears 531, as shown in FIG. 21. During the continued backstroke of the needles 60, the strands 700 are pulled from the grooves 605 and remain in this position throughout the complete backstroke of the machine. Substantially equal tension is maintained on the strands during the backstroke which is completed after the needles'60 have been withdrawn from the grid wall 510, as shown in FIG. 22.

. After the needles 60 have been fully withdrawn from the grid wall 510 at the upper end of the backstroke, the pawl 212 engages the next groove 552 and indexes or pushes the grid box 500 forward to the next sewing position; the grid box 500 is prevented from overfeeding by the brake 45. During the advancing motion of the grid box 500 the notches 518 align the strands 700 for the next sewing cycle. The forward motion of the needles 60 starts to repeat the sewing cycle, and the strands 700 automatically align themselves in the needle slots 605 as a result of the pre-alignment of the strands 700 by the notches 518, as shown in FIGS. 22

and 24. The sewing-indexing operation automatically' proceeds until the strands are sewn in each of the aligned dual passages 514-524 by the row of needles 602. After the last row or dual grid passages 514-524 is sewn, the edge rods 550 have been indexed past the table hole 214 so that the pawl 212 contacts the corner bracket 540 as it starts its upward travel. The bracket 540 prevents the pawl 212 from completing its predetermined travel thereby causing the switch 210a to stop the machine at the end of the last sewing operation.

The strands 700 are secured to the grid box 500 by a U-shaped spring clip (not shown) in slots 560; similar to the manner in which the strands were initially secured to the grid box 500. The strands 700 are then cut deparating the needles 60 and] the grid box 500. Thus, this completes the sewing of the grid box in the first of three directions; or in other words, the grid box has strands 700 laced in the X direction.

The grid box 500 is turned 90on the feed table 20 with the complete sewing operation described hereinabove repeated, thereby completing the sewing of the grid box 500 in the second direction; the grid box 500 i now having strands also in the Y direction. Again, the box 500 is turned 90on the feed table 20 with the operations described hereinabove again repeated, thereby completing the sewing of the grid box 500 in the third direction; thus, thegrid box 500 now has strands 700 in the X, Y and Z directions and is capable of use a three dimensional reinforcement. When the sewing operation is performed when the relationship between the table and the needle motion issubstantially perpendicular then the lattice will be substantially orthogonal.

The amount of prestressing or tensioning of the strands can be controlled by the force required to pull the strands from their spools on the creel coupled with the cooperative interaction of the dancer roll 704 and the spring tensioned shaft. It has been found that the edge rods 550 and the snap rings 543 may be removed after the three dimensional lattice has been sewn and long as the edge rods 550 define exterior surfaces that are substantially planar forming a box such as a parallele-piped. Since the grid surface openings can be made any desired cross directional configuration, needles having a similar cross sectional configuration can be used therewith. It is also contemplated that the needles can sew one or more strands, as desired. It has been found that any type of strand :inaterial may be used as long as it is sufficiently flexible for the size of the needles and the size of the grid box used. It is also contemplated that the strand material and different sizes of strands may be mixed while sewing the grid in one direction; or, alternatively, the :strands in one direction can be of different size and material than the strands in any other direction.

Although specific embodiments of the invention have been described, many modifications and changes may be made in the machine and the companion grid structure without departing from the spirit and scope of the invention as defined in the appended claims.

What is claimed is:

1. A-structure for maintaining a three dimensional lattice array of strands comprising:

1 six grid wall surfaces, three of the surfaces substantially of one configuration and the other three surfaces of another specific configuration;

2. means holding the grid surfaces in a hollow shaped configuration; and

3. means for securing a lattice array of strands inbetween the grid wall surfaces.

2. The structure of claim 1 wherein the holding means comprise edge rods.

3. The structure of claim 1 wherein the securing with strands in a three dimensional array. means comprise lugs with ears on at least one grid wall 5. The structure of claim 1 wherein the holding and notches on the opposite grid wall. means comprises laced strands.

4. The structure of claim 3 wherein the box is laced 

1. A structure for maintaining a three dimensional lattice array of strands comprising: 1 six grid wall surfaces, three of the surfaces substantially of one configuration and the other three surfaces of another specific configuration;
 2. means holding the grid surfaces in a hollow shaped configuration; and
 3. means for securing a lattice array of strands inbetween the grid wall surfaces.
 2. means holding the grid surfaces in a hollow shaped configuration; and
 2. The structure of claim 1 wherein the holding means comprise edge rods.
 3. The structure of claim 1 wherein the securing means comprise lugs with ears on at least one grid wall and notches on the opposite grid wall.
 3. means for securing a lattice array of strands inbetween the grid wall surfaces.
 4. The structure of claim 3 wherein the box is laced with strands in a three dimensional array.
 5. The structure of claim 1 wherein the holding means comprises laced strands. 